In prior art, the heat dissipation module is usually mounted on a bracket which is fixed on a CPU platform via spring screws. Although this configuration can fix the heat dissipation module in place, the use of it has a certain limitation. For example, this configuration is not adaptive to an AMD system, and the installation of the heat dissipation module and the bracket is inconvenient. Thus, it is desirable to provide a retainer which is able to overcome the above issues.